String Concatenation in Java

String Concatenation 

In java, string concatenation forms a new string that is the combination of multiple strings. There are two ways to concat string in java:

1. By + (string concatenation) operator
2. By concat() method

1) String Concatenation by + (string concatenation) operator

Java string concatenation operator (+) is used to add strings. For Example:

1. class TestStringConcatenation1{  
2.  public static void main(String args[]){  
3.    String s="Sachin"+" Tendulkar";  
4.    System.out.println(s);//Sachin Tendulkar  
5.  }  
6. }  

Output

Output:Sachin Tendulkar

The Java compiler transforms above code to this:

1. String s=(new StringBuilder()).append("Sachin").append(" Tendulkar).toString();  

In java, String concatenation is implemented through the StringBuilder (or StringBuffer) class and its append method. String concatenation operator produces a new string by appending the second operand onto the end of the first operand. The string concatenation operator can concat not only string but primitive values also. For Example:

1. class TestStringConcatenation2{  
2.  public static void main(String args[]){  
3.    String s=50+30+"Sachin"+40+40;  
4.    System.out.println(s);//80Sachin4040  
5.  }  
6. }  

Output

80Sachin4040

2) String Concatenation by concat() method

The String concat() method concatenates the specified string to the end of current string. Syntax:

1. public String concat(String another)  

Let's see the example of String concat() method.

1. class TestStringConcatenation3{  
2.  public static void main(String args[]){  
3.    String s1="Sachin ";  
4.    String s2="Tendulkar";  
5.    String s3=s1.concat(s2);  
6.    System.out.println(s3);//Sachin Tendulkar  
7.   }  
8. }  

Output

Sachin Tendulkar